The Different Types of Chelation Agents

There are many important biological chemicals which are known as Chelation Agents. These agents play important roles in oxygen transport and in photosynthesis. There are also many biological enzymes which are chelation agents too.

In addition to their importance in living organisms, chelates are also reasonably important, both as products in themselves and as agents in the production of their chemicals.

A chelate is a chemical mixture of a metal ion and a chelating agent. A chelating agent is a substance whose molecules can form different bonds to a single metal ion. An example of a simple chelating agent is ethylenediamine.

Water is not a chelating agent. Because the chelating agent is closed to the metal ion by different bonds, chelates tend to be more stable than complexes formed monodentate ligands such as water.

Potphine is a chelating agent like ethylenediamine in that it forms bonds to a metal ion through nitrogen atoms. Each of the four nitrogen atoms in the center of the molecule can form a bond to a metal ion. Porphine is the simplest of a group of chelating agents called porphyrins. Porphyrins have a formation derived from porphine by replacing some of the hydrogen atoms around the outside with other groups of atoms.

 One important porphyine chelate is heme, the central component of hemoglobin, which carries oxygen through the blood from the lungs to the tissues.

 Another biologically significant chelate is vitamin B-12. It is the only vitamin that contains a metal; it is required in the diet of all higher animals. It is not synthesized by eitherhigher animals or plants, but only by certain molds and bacteria.

A chelating agent of particular economic significance is ethylenediaminetraacetic acid which is known as EDTA.

EDTA is a resourceful chelating agent. It can form four or six bonds with a metal ion, and it forms chelates with both transition-metal ions and main group. EDTA is normally used in detergents and soaps, because it forms complexes with magnesium ions and calcium. EDTA is also used widely as a stabilizing agent in the food industry. Food spoilage is often promoted by naturally occurring enzymes that contain transition metal ions.

Dimercaprol is also an effective chelating agent for heavy metals such as mercury, gold, antimony and arsenic. It was basically used to treat the effects of an arsenic containing mustard gas called Lewisite, which was used in World War1. 

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